Frank Gollan

Survival of Mammals Breathing Organic Liquids Equilibrated with Oxygen at Atmospheric Pressure

Because oxygen and carbon dioxide are very soluble in certain silicone oils and fluorocarbon liquids, these liquids will support respiration of mammals. Mice and cats respiring silicone oil die shortly after return to air breathing, while those breathing fluorocarbon survive for weeks. The respiration of mice is optimally supported by these organic liquids at about 20�C. In cats, arterial oxygenation is excellent, but there is some impairment of carbon dioxide elimination. All animals have suffered some pulmonary damage from breathing fluorocarbon liquids. Continued investigation of organic fluid respiration may lead to development of a safe method to support the respiration of man by liquids equilibrated with gases at atmospheric pressure.

Intramedullary Pressure and Pulmonary Embolism of Femoral Medullary Contents in Dogs during Insertion of Bone Cement and a Prosthesis

Femoral medullary pressures and pulmonary embolization of medullary contents during the insertion of cement and a medullary rod in greyhounds were studied. In three animals, insertion of cement into the femoral shaft resulted in medullary pressures of between 290 and 900 torr and the appearance of medullary contents in the lungs within ten to 120 seconds. In five other animals, pulmonary embolization was not detectable when the rise in femoral medullary pressure was prevented by drilling a hole distal to the cemented area.

ELECTRICAL IMPEDANCE OF PULSATILE BLOOD FLOW IN RIGID TUBES AND IN ISOLATED ORGANS

The present concept underlying electrical impedance rheography holds that the wave of conductive blood perfusing the resistive tissue cells causes an increase of conductivity or a decrease in electrical impedance.’ Until now it has not been possible to convert this seemingly simple bioelectrical event into a reliable clinical method because it still lacks the main prerequisite of a scientific method; i.e., it cannot be quantitated reproducibly in absolute physical units. Despite the plethora of mathematical theorems on the one hand, and of diligent clinical empiricism on the other, there is a scarcity of animal experimentation to prove or to disprove the present concept. One century after the publication of Claude Bernard’s Introduction to the Study of Experimental Medicine, there is certainly nothing unusual in taking an indirect and variable method, like clinical impedance rheography, out of its impenetrable clinical complexity and subjecting it to controlled experimentation. This is the only way open to us to distinguish between coincidence and cause, between statistical and biological significance, or between the propter hoc and the ergo hoc. It is unusual, however, that miles of paper have rolled off from a variety of instruments in Europe and on this continent for the last three decades without experimental evidence of the hemodynamic cause of the measured phenomenon. The first part of the present studies was devised in an effort to define the factors influencing impedance pulses in rigid tubes by changing the blood perfusate. The second part of the studies deals with the hemodynamic factors producing the tissue electrical impedance waves in mechanically perfused isolated organs. Such a system permits the control of total inflow, stroke volume, pulse pressure, pulse rate, and composition of the perfusate.

Basic studies in rheoencephalography

A REVIEW of the literature classified under the heading of rheoencephalography between 1959 and 1964 reveals some 150 articles and at least 1 book. Despite this scientific fecundity, there is still poor understanding of the cause and significance of the waves which can be recorded from electrodes attached to the scalp when an alternating current of low intensity ( 2 to 15 ma.) is passed through them. The present concept holds that the impedance or the resistance of the head to an electric current varies according to the pulsatile flow of blood. Since the electrical impedance of blood, containing about 45% highly resistive cells and about 55% highly conductive plasma, is much lower than that of the surrounding cells, the pulse wave causes a drop in tissue impedance. It has been held that alterations in the form or magnitude of the recorded waves of impedance changes are in some way related to blood flow. These studies were devised in an effort to study the origins of these recorded waves and their relation to cerebral blood flow. We have been partidarly interested in correlating rheoencephalography (REG) with a variety of simultaneous measurements of cerebral blood flow in experimental animals and in man.

Effect of the Skeletal Muscle Relaxant Dantrolene Sodium on the Isolated, Perfused Heart

Summary The literature indicates that dantrolene sodium has produced negligible cardiovascular changes in intact dogs and in patients, but caused depression in the isolated perfused heart. In nine consecutive experiments rat hearts were perfused by means of a modified Langendorff preparation with 3.5% bovine albumin in buffered, mammalian Ringers solution. Perfusion pressure and temperature were kept constant. Flow was measured with an infrared drop counter. Continuous recordings were made of heart rate, coronary flow, resting length, intraventricular pressure, force displacement and their first derivatives. Statistical analysis of all parameters before and during the perfusion with dantrolene sodium solution showed no significant changes for the same period of time. These results show that dantrolene sodium has no effect and do not confirm recent publications which reported a marked myocardial depression by dantrolene sodium.

Oxygen transport and delivery in rabbits treated with cyanate

Summary Oxygen transport, delivery and utilization were compared in normal and cyanate-treated rabbits made progressively more anemic by isovolemic replacement of blood by a buffered albumin solution. Oxygen delivery, consumption, and utilization did not differ significantly between the two groups of animals at packed cell volumes of over 20% to less than 5% despite the marked left shift in the oxyhemoglobin dissociation curve in the animals treated with cyanate. Since there was no evidence of tissue hypoxia in the latter group, it is concluded that tissue hypoxia will also not be seen in patients treated with smaller doses of sodium cyanate.

Total hypothermic blood exchange in acute endotoxin shock

It has been reported that total hypothermic blood exchange holds promise for the treatment of septic shock in animals. Since this procedure does not carry any mortality in out laboratory, we studied its effect in an acute septic shock model. After the intravenous injection of endotoxin (10 mg/kg) and blood transfusions into 33 dogs, severe haemoconcentration, tachypnoea, tachycardia, low cardiac output, metabolic acidosis and hyperpyrexia led uniformly to death within 5 h. All of these symptoms were prevented in five dogs by total hypothermic blood exchange, instituted 5 min after the endotoxin injection. Nevertheless, all of these treated animals died a delayed death. Since the endotoxin particles are rapidly phagocytosed by the reticulo-endothelial system, even very early total blood exchange cannot dislodge them from their intracellular site.

Experimental study of perfusion of rabbits with fluorocarbon fluid in the acute asanguineous state

Abstract Gases are extremely soluble in fluorocarbon fluids and therefore they can serve as respirator media in intact animals. In the form of fine emulsions they can substitute for the gas-exchange function of red cells in isolated, perfused organs. Rabbits were anaesthetized with Nembutal and respired with room air. In six of them the blood was exchanged slowly for an iso-osmotic, buffered plasma-expander, and in nine other rabbits it was exchanged for 10% or 20% fluorocarbon emulsified into the plasma-expander. The diameters of about 90% of the fluorocarbon microspheres were in the range 1·5–5 μm. In both groups the haematocrit was lowered to less than 5%. Throughout the procedure, measurements were made of arterial and venous PO 2 PCO 2 , pH, oxygen content, oxygen extraction, standard bicarbonate, left ventricular pressure, central venous pressure, heart rate and temperature. None of these parameters, nor the survival time of about 30 min, showed a statistically significant difference between the two groups of severely anaemic animals. The cause of death was myocardial depression. It was concluded that the inefficiency of fluorocarbon emulsions to deliver oxygen to the tissues of intact animals was probably due to the presence of protein molecules in concentrations as low as a few micrograms per 100 ml, which could change the tension of the water-fluorocarbon interface. In perfused small organs or organisms the protein content is probably too low to block oxygen diffusion from the fluorocarbon particles.

Experimental Analysis of the Rheoencephalogram (REG).

Summary 1. Controlled perfusion of the head of dogs through the common carotid arteries by means of a pump-oxygenator, produces electrical impedance changes. 2. If pulsatile flow is made continuous, these electrical impedance changes disappear. 3. The electrical impedance pulses are independent of pressure and directly related to stroke volume. 4. Since changes of electrical conductivity occur in blood moving in rigid tubing or in a beaker, pulse volume changes may not be the cause of the observed electrical impedance pulses. Therefore, it is suggested that instead of the misleading and cumbersome name of electrical impedance plethysmography, the more general and shorter name of electrical rheography be used.

Effect of certain liquid organopolysiloxanes on cholesterol atherosclerosis of the rabbit.

Summary Addition of dimethylpolysiloxane to a diet containing 2% cholesterol does not alter hypercholesterolemia and cholesterol content of the liver of rabbits. However, it increases cholesterol content of the aorta and produces atheromatous lesions of the intima. Addition of phenylmethyl-polysiloxane to a diet containing 2% cholesterol prevents severe hypercholesterolemia and increases cholesterol content of the liver. It lowers the cholesterol content of the aorta and prevents atheromatous proliferation.